The present invention relates to a numerical analysis mesh generating method and apparatus for a CAE (Computer Aided Engineering) system which relies on a computer-based numerical simulation to optimize and rationalize design works, and more particular to a method for readily generating an analysis mesh when a geometric model under analysis has been changed.
As conventional techniques for readily creating an analysis mesh when a three-dimensional geometric model under analysis has been changed, there are following methods.
JP-A-4-074280 shows a method (first method) which reads a numerical analysis mesh registered in a previously created model file, receives a correspondence relationship, specified by a system user between nodes of boundaries on the numerical analysis mesh and constituent points of a geometric model for which a mesh is newly created, and creates nodes internal to the geometry to create an analysis mesh.
JP-A-6-068217 shows a method (second method) which references geometry-to-mesh correspondence data when the dimension of a feature such as the width of the feature, the diameter of a hole, or the like is changed in a geometric model under analysis, and uses a coordinate conversion matrix from a coordinate system for the geometric model before the feature is changed to a coordinate system after the feature is changed to modify an analysis mesh for the portion subjected to the changed feature, and then smooth node coordinate values to create an analysis mesh.
JP-A-8-212240 shows a method (third method) which, when a hole feature is added due to a design change, previously creates an analysis mesh for the hole portion, moves the analysis mesh for the hole portion to a location at which a modification is desired in the previously created analysis mesh, and collectively calculates differences between the previously created analysis mesh and the analysis mesh for the hole portion to create an analysis mesh.
U.S. Pat. No. 5,892,515 in turn shows a method which creates a mapping model from a geometric model to create an analysis mesh.
The above-mentioned prior art methods for creating an analysis mesh when a geometric model under analysis is changed have the following problems.
The first and second methods, although having the ability of supporting a design change such as a change in dimension of a feature, cannot create an analysis mesh when a design change involves a different topological relationship such as a connection between edges, a connection between surfaces or the like of a geometric model.
The first method also requires the system user to specify a correspondence relationship between nodes of boundaries in a numerical analysis mesh and constituent points in a geometrical model for which a mesh is newly created, thereby resulting in an increased number of mesh creation steps.
The third method requires the system user to interactively place the mesh for the hole portion on the previously created geometric model, and may result in creating a mesh which has an undesirable feature from a viewpoint of analysis depending on a positional relationship between the previously created mesh and the mesh for the hole portion, due to the collective calculation of the differences between the previously created analysis mesh and the analysis mesh for the hole portion.
It is an object of the present invention to provide a numerical analysis mesh generating method and apparatus which are capable of efficiently creating a high quality hexahedral mesh for highly accurate analysis and reducing a total calculation cost. More particularly, it is an object of the present invention to provide a numerical analysis mesh generating method and apparatus which are capable of readily creating a high quality analysis mesh when a geometric model under analysis is changed in a mesh generating method using a mapping approach.
To achieve the above object, the present invention provides a numerical analysis mesh generating method comprising the steps of inputting a geometric model under analysis, selecting a verification model having the geometry analogous to the geometric model, corresponding the geometric model to the verification model in terms of the geometry, reading a previously created mapping model approximated from the verification model with a lattice, modifying the mapping model of the verification model using a geometric correspondence between the geometric model and the verification model to create a mapping model for the geometric model, and mapping lattice points in the created mapping model for the geometric model to the geometric model to create a numerical analysis mesh.